Propylthiouracil Compounded Oral Suspension

This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition

Issued and maintained by the United States Pharmacopeial Convention (USP)

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1 DEFINITION

Propylthiouracil Compounded Oral Suspension contains NLT 90.0% and NMT 110.0% of the labeled amount of propylthiouracil (C₇H₁₀N₂OS).

Prepare Propylthiouracil Compounded Oral Suspension 5 mg/mL as follows (see Pharmaceutical Compounding—Nonsterile Preparations 〈795〉).

ᵃ Propylthiouracil 50-mg tablets, West-Ward Pharmaceutical Corp., Eatontown, NJ.

ᵇ Paddock Laboratories, Minneapolis, MN.

Calculate the required quantity of each ingredient for the total amount to be prepared. Place the required number of Propylthiouracil tablets in a suitable mortar, and comminute to a fine powder with a pestle. Add the Vehicle in small portions, and triturate to make a smooth paste. Add increasing volumes of the Vehicle to make a propylthiouracil liquid that is pourable. Transfer the contents of the mortar, stepwise and quantitatively, to a calibrated bottle. Add enough of the Vehicle to bring to final volume, and mix well.

2 ASSAY

Change to read:

2.1 Procedure

Mobile phase: 5 mM 1-heptanesulfonic acid sodium salt, glacial (USP 1-Aug-2020) acetic acid (1% v/v), and methanol (40:45:15). Pass through a nylon 66 filter of 0.45-µm pore size, and degas.

Internal standard solution: 1.0 mg/mL of 6-methyl-2-thiouracil in methanol

Standard stock solution: 1.75 mg/mL of USP Propylthiouracil RS in methanol

Standard solution: Pipet 0.4 mL of the Standard stock solution into a 10-mL volumetric flask, and add 0.25 mL of the Internal standard solution. Dilute with Mobile phase to volume to obtain a nominal concentration of 70 µg/mL of propylthiouracil and 25 µg/mL of 6-methyl-2-thiouracil, and centrifuge.

Sample solution: Shake thoroughly by hand each bottle of Oral Suspension. Pipet 2 mL of Oral Suspension into a 10-mL volumetric flask, and dilute with methanol to volume to obtain a concentration of 1 mg/mL. Transfer 0.7 mL of the diluted solution to a 10-mL volumetric flask, and add 0.25 mL of the Internal standard solution. Dilute with Mobile phase to volume to obtain a nominal concentration of 70 µg/mL of propylthiouracil and 25 µg/mL of 6-methyl-2-thiouracil, and centrifuge.

Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: UV 276 nm

Column: 3.0-mm × 15-cm; 5-µm packing L1

Column temperature: 40°

Flow rate: 0.4 mL/min

Injection volume: 10 µL

System suitability

Sample: Standard solution

[Note—The relative retention times for 6-methyl-2-thiouracil and propylthiouracil are about 0.25 and 1.0, respectively.]

Suitability requirements

Resolution: NLT 10.0 between propylthiouracil and 6-methyl-2-thiouracil

Column efficiency: NLT 10,000 theoretical plates

Tailing factor: NMT 2.0 for the propylthiouracil peak

Relative standard deviation: NMT 2.0% for replicate injections

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of propylthiouracil (C₇H₁₀N₂OS) in the portion of Oral Suspension taken:

Result = (R_U/R_S) × (C_S/C_U) × 100

R_U = peak response ratio of propylthiouracil to the internal standard from the Sample solution

R_S = peak response ratio of propylthiouracil to the internal standard from the Standard solution

C_S = concentration of USP Propylthiouracil RS in the Standard solution (µg/mL)

C_U = nominal concentration of propylthiouracil in the Sample solution (µg/mL)

Acceptance criteria: 90.0%–110.0%

3 SPECIFIC TESTS

pH 〈791〉: 3.8–4.8

4 ADDITIONAL REQUIREMENTS

Packaging and Storage: Package in tight, light-resistant containers. Store at controlled room temperature or in a refrigerator.

Beyond-Use Date: NMT 90 days after the date on which it was compounded, when stored in a refrigerator, and NMT 60 days after the date on which it was compounded, when stored at controlled room temperature

Labeling: Label it to indicate that it is to be well shaken before use, and to state the Beyond-Use Date.

USP Reference Standards 〈11〉

USP Propylthiouracil RS